The broad objective of the research is to provide reliable documentation of the infant's developing ability to discriminate and comprehend the emotional expressions of others. It focuses specifically on three as yet unresolved questions: (1) When do infants detect the distinctive facial configurations relevant to adult's judgements of emotion? (2) Are young infants more sensitive to realistic (dynamic, multimodal) than to static presentations (photographs, drawings) of emotional expression. and (3) When and in what way do infants understand the "meaning" conveyed by a facial expression? With respect to Question 1, independent groups of 4-, 5-1/2-, and 7-month-old infants will be required to recognize and invariant facial expression displayed in photographs despite changes in person and in feature (e.g., whether a smile is "toothy" or closed-mouth). Regarding Question 2, infants of the same age will be required to do the same but when the expressions are displayed in videotaped episodes--with any without sound. Finally, as to Question 3, infants of 7, 9-1/2, and 12 months plus any younger groups to have successfully discriminated in studies 1 and 2 will be tested on their ability to "match" a facial expression to (a) its approproate gestural and vocalic accompaniments, (b) the behavior it typically signals, and (c) the circumstances thst customarily evoke it. Standard familiarization-novelty techniques will be used with the static material, and modifications thereof with the dynamic stimuli of studies 2 and 3. The research should have substantive impact on basic issues in perceptual, socioemotional, and cognitive development as well as pragmatic implications for the quality of the infant-caregiver relationship.